Peripheral neuropathies are a group of diseases characterized by the damage and, therefore, by the malfunction of the peripheral nerves. The peripheral nervous system is made up of the nerves that connect the central nervous system (brain and spinal cord) to muscles, skin and internal organs.
According to the type of fibers they contain, peripheral nerves are divided into three types:
- engines, they control the muscles and are responsible for voluntary movements
- psychics, transmit sensations, such as pain, touch, temperature, vibrations
- vegetative or autonomic, control involuntary or automatic functions of the body, such as heart rate, blood pressure, digestive functions
Some neuropathies appear suddenly, others gradually over a period of years. The disease can affect a nerve (mononeuropathy, usually of traumatic origin), two or more nerves in different areas (multineuropathy, usually of vascular origin) or many nerves (polyneuropathy, usually of toxic, metabolic, vitamin deficiency or inflammatory origin).
The disorders (symptoms) depend on the type of nerve fibers involved and their location; in most cases they manifest themselves with weakness, tingling and pain. Many neuropathies affect all three types of nerve fibers to varying degrees; others, just one or two.We therefore speak of purely or predominantly motor, sensory or vegetative neuropathies.
The disorders (symptoms) vary according to the type of nerve involved (motor, sensory, vegetative) and its location.
The disorders caused by sensory neuropathy can be very different and include:
- pins and needles
- stinging sensation such as needles or pins or pinching in the affected parts
- painful twinges
- electric shocks
- numbness and reduced ability to feel pain or changes in temperature
- loss of balance and coordination, caused by the inability to perceive the position of parts of your body. You may also have the sensation of wearing gloves or socks, when your hands and feet are bare
Disorders caused by motor neuropathy include:
- muscle twitching and cramps
- muscle weakness
- paralysis of one or more muscles
- foot drop (difficulty lifting the front of the foot and toes, particularly when walking)
Autonomic or vegetative neuropathy
Disorders caused by autonomic or vegetative neuropathy include:
- constipation or diarrhea
- abdominal bloating and belching
- low blood pressure (arterial hypotension)
- dizziness and fainting feeling when standing up
- rapid heartbeat (tachycardia)
- excessive sweating or lack of sweat
- thinning of the skin, easily bruising and difficulty healing wounds
- sexual dysfunctions
- difficulty emptying your bladder completely
The disturbances caused by the mononeuropathy depend on the type of nerve damaged and include:
- altered sensations
- double vision or other vision problems, sometimes with eye pain
- facial palsy (Bell's palsy)
The most common type of mononeuropathy is carpal tunnel syndrome which affects a small tunnel located in the wrist. In carpal tunnel syndrome, the part of the median nerve that passes through the tunnel is compressed; its compression can result from excessive use of the wrist or from inflammatory processes and can cause pain, tingling and numbness in the fingers.
Bell's palsy is a disorder of the facial nerve, the nerve that contains motor fibers, for the mimic muscles of the face, and vegetative fibers. Paralysis usually manifests itself with asymmetry of the lips (crooked mouth) and difficulty in closing the eye on the same side, but hearing (hyperacusis) and taste disturbances can also be associated. In most cases, spontaneous healing occurs over a longer or shorter period (from one to several months).
Based on the multiple causes that determine them, peripheral neuropathies can be divided into:
- acquired neuropathies, due to other diseases, to the intake of certain drugs or to events that occur in the course of life
- hereditary neuropathies, caused by genetic abnormalities
Most neuropathies are acquired, and can be due to different causes. When the cause of the neuropathy is not known, it is referred to idiopathic neuropathy.
- diabetes, is one of the most common causes of neuropathy. Neuropathy caused by type 1 diabetes or type 2 diabetes is called diabetic neuropathy. It occurs during the course of the disease and is probably caused by the high concentration of sugar (glucose) in the blood (high blood sugar) which damages the small blood vessels that supply the nerves. It is a predominantly sensory neuropathy, which can be associated with autonomic disorders and alterations of the cranial nerves.
In the presence of diabetes, the risk of neuropathy increases if blood sugar is not controlled, if you smoke or regularly consume large quantities of alcohol
- alcohol and other toxic substances, alcohol abuse is a frequent cause of neuropathy. Other toxic substances that can damage nerves are arsenic, lead, mercury, organic solvents and insecticides
- nutritional deficiencies, vitamin B12 deficiency or other vitamins (B1, B6, vitamin E) can cause polyneuropathies. Vitamin deficiency may be due to an inadequate diet or a malabsorption problem in the stomach or intestines. An excess of vitamin B6 can also cause neuropathy
- neuropathies in the course of diseases that affect the whole organism, in addition to diabetes, numerous other diseases can be associated with neuropathy. Persistent (chronic) kidney or liver disorders over time can cause a large amount of toxins to build up in the body, damaging nerve tissue; in case of hypothyroidism, the body does not produce enough thyroid hormone, resulting in fluid retention and increased pressure in the nerve tissues damaging them
- immune-mediated neuropathies, are caused by alterations in the body's defense system (immune system)
- Guillain-Barrè syndrome, is a rare, rapid onset condition. It is often preceded by infections which are considered to be triggers. The severity and duration of the disease range from mild weakness, usually associated with spontaneous recovery, to total paralysis (quadriplegia) with respiratory failure. A variant of Guillain-Barrè syndrome is Miller-Fisher syndrome, which manifests itself with drooping of the eyelids (eyelid ptosis) and unstable (ataxic) gait.
- chronic inflammatory demyelinating polyradiculoneuropathy, is a sensory-motor disease that affects both sides of the body.It is characterized by its permanence over time (chronic course) and can often lead to severe disability; an autoimmune cause is suspected
- multifocal motor neuropathy, is a rare autoimmune disease (in autoimmune diseases the body's defense system does not recognize the organs and tissues as its own and attacks them) that affects the motor nerves
- neuropathies associated with vasculitis, vasculitis is an inflammation of the blood vessels. If the inflammatory process affects the vessels supplying the peripheral nerves, it can damage the nerves causing vasculitic neuropathy. Several rheumatological diseases, such as rheumatoid arthritis, systemic lupus erythematosus, panarteritis nodosa, or Sjogren's syndrome are associated with generalized vasculitis that can also involve peripheral nerves
- neuropathies associated with monoclonal gammopathies, in monoclonal gammopathies there is the abnormal growth (proliferation) of B lymphocytes or plasma cells that expand to form tumors, benign or malignant, producing antibodies; the latter, in some cases, react against some components of the peripheral nerves, causing neuropathies
- tumors, some types of cancers, such as lymphomas or multiple myeloma, can infiltrate the nerves and cause neuropathy through direct damage. Tumors can also cause neuropathy through an indirect effect; in this case we speak of paraneoplastic syndrome and neuropathy is caused by an immune mechanism: in practice, the immune system recognizes molecules, called antigens, shared by both the tumor and the cells of the nervous system and attacks them. In people with cancer, a neuropathy can also be the result of local radiation therapy or be caused by drugs such as vincristine and cisplatin. In these cases, we speak of iatrogenic neuropathies
- infectious agents, both viruses and bacteria can cause neuropathies.Viruses include herpes zoster, responsible for fire of S. Antonio, the AIDS virus (HIV), cytomegalovirus (CMV), especially in people with impaired immune system function (immunosuppressed people). Hepatitis B and C are also sometimes associated with neuropathy. Among the bacterial infections we remember Lyme disease (borreliosis), caused by a bacterium that infects ticks, leprosy, diphtheria
- medications, peripheral neuropathy, in some people, may appear as a side effect of some medications. They include: some cancer medicines; nitrofurantoin, used in some chronic kidney diseases; amiodarone, used in heart arrhythmias; disulfiram, used in alcoholism; dapsone, used in the treatment of leprosy; some antibiotics (metronidazole, nitrofurantoin) and phenytoin, an anticonvulsant, when taken for long periods
- trauma or compression, trauma or compression caused by tendons or other surrounding tissues can lead to neuropathies. The best known are: carpal tunnel syndrome, which derives from compression of the median nerve at the wrist, and cervical and lumbo-sacral radiculopathies (the latter known as sciatica) due to the compression of the nerve roots at their point of exit at the level of the spinal column. Other areas of frequent compression of the nerves are the elbow, the armpit and the back of the knee
The term idiopathic it is used when the cause of the neuropathy has not been identified.
- Charcot-Marie-Tooth disease (also called hereditary sensory-motor neuropathy), and other types of hereditary sensory-motor neuropathies are the most frequent hereditary neuropathies. Different subtypes are distinguished on the basis of the disorders they cause and the type of genetic alteration that underlies them
- familial amyloidotic neuropathy, consists of sensory and vegetative nervous system alterations. It is due to the mutation of a protein called transthyretin; the abnormal protein is deposited in the form of amyloid in the peripheral nerves, damaging them
- porphyria (hereditary disease due to altered metabolism of porphyrins), associated with a peripheral neuropathy mainly of the motor type
The assessment (diagnosis) of neuropathy and its causes is essential to define the most effective therapy to treat it. The referring specialist is the neurologist.
To ascertain the presence of neuropathy (diagnosis) the doctor inquires about the present and past state of health, evaluates the disorders (symptoms) and their possible causes (for example, exposure to toxic substances, drug intake).
He may also order some laboratory tests to help identify the cause of the neuropathy. The most important are:
- electromyogram and study of the conduction velocities of nerve fibers, to know the functional state of the nerves and to identify the affected nerves and the distribution of damage
- nerve or muscle biopsy, to obtain information on the type and cause of neuropathy. To check, for example, if the nerve shows signs of vasculitis, inflammation or amyloid deposition
- cerebrospinal fluid examination, obtained by lumbar puncture, to highlight the presence of infections or inflammation
- targeted blood and urine tests, to identify underlying diseases, vitamin deficiencies or genetic defects underlying the neuropathy
To define the causes of neuropathy it may also be necessary to perform:
- radiography, X-ray examination
- computed tomography (CT)
- magnetic resonance imaging (MRI)
Treatment of peripheral neuropathy depends on the disorders (symptoms) present and the underlying causes.
In the diabetes, careful control of hyperglycemia helps slow the progression of neuropathy.
A vitamin deficiency it can be corrected by administering the missing vitamin.
Any infections they can be treated with antibiotics or antiviral drugs.
The autoimmune diseasesoften respond to plasmapheresis (a procedure in which blood is removed from the body, cleared of harmful molecules such as autoantibodies, and finally reintroduced into the body), to immunosuppressive therapies or immunomodulators that block the immune system response (corticosteroids, intravenous immunoglobulins, or chemotherapy).
In the paraneoplastic neuropathies (which are associated with a tumor and, sometimes, precede its discovery) the treatment is aimed at eliminating the underlying tumor.
The drug-induced or toxic-agent-induced neuropathies they are cured by removing the agent that caused them.
Depending on the cause, the treatment can relieve, slow or heal the neuropathy. If the damage is blocked, the nerve can regenerate. Since the degree of recovery depends on the extent of the damage, it is very important to ascertain the cause of the neuropathy as soon as possible and to start therapy immediately.
The main disorders (symptoms) caused by neuropathies are:
- muscle weakness
Pain can be relieved with analgesic medications. Physiotherapy and physiotherapy tools can help maintain muscle strength and improve movement.
Italian Association of Peripheral Neuropathies (AINP) Onlus
NHS. Peripheral neuropathy (English)